Garden Talk: March 24, 2011

From NGA Editors

Go Back to School and Grow Green

Youngsters may be looking ahead eagerly to the start of summer vacation, but perhaps gardeners should be thinking about going back to school -- to the Lawncare University, that is.

Lawncare University is a new DVD put together by the Turf Team at Michigan State University. Divided into spring, summer, fall, and turf grass pests segments, the DVD provides great information for home gardeners on mowing, fertilization, weed control, irrigation, dealing with weeds, insect pests, and moles, and much more. Most of the video segments have an accompanying written bulletin that can be downloaded for free. The price for the DVD is $19.95, which includes shipping within the U.S.

Also available at the MSU Turf Web site is a free lawn care tip sheet to download with advice on how to go green while you grow a green lawn. Recommendations include mowing grass at least 3 inches high to crowd out weeds and promote deeper, more drought-tolerant root systems. Leave clippings on the lawn to recycle nutrients, sweeping any that land on walks and driveways back onto the turf.

Lots more helpful lawn care information is available on-line, including information on identifying turf weeds, lawn care without pesticides, and fertilizing home lawns to protect water quality.

Better Biocontrol in the Future

While none of us want to see our gardens decimated by insect pests, few of us want to control pests with toxic sprays that can harm us and the environment. So it's encouraging to learn of the progress researchers at the USDA's Agricultural Research Service are making in improving on the well-known microbial insecticide called B.t.

Short for Bacillus thuringiensis, this environmentally friendly bacterial pesticide is used to control caterpillars of all sorts both by home gardeners and commercial growers and farmers. But the most commonly used strain, B. t. kurstaki, only survives for one generation. After the initial pest infestation is killed, the bacteria die out, leaving no protection against future infestations.

Entomologist Michael Blackburn tested 50 strains of B.t. known to be toxic to the larvae of gypsy moths and found they could be divided into two groups based on their ability to produce an enzyme called urease. He fed all the strains to gypsy moth larvae; when the larvae died they were ground up and applied to food pellets that were then fed to a new generation of caterpillars. He discovered that the strains that produced the enzyme survived better over the course of repeated feedings than those without. Most of the urease-producing strains survived five successive passages through gypsy moth larvae.

It is hoped that this research will pave the way for the development of more effective B.t. strains, perhaps ones that will be able to grow on mulch, multiply on specific crops, and persist in gardens. The development of such long-lasting biocontrol would be a boon to gardeners and a big benefit to the environment.

Vanishing Farmland

Our country is so vast that it's easy to think we don't have to worry as housing developments and highways spring up to cover the land. But figures released by the American Farmland Trust regarding the National Resources Inventory are sobering. The Inventory is a survey of the nation's non-federal lands conducted by the USDA's Natural Resources Conservation Service in cooperation with Iowa State University to document conditions and trends in natural resources, including loss of agricultural land to development.

It found that, in the period from 1982 to 2007, more than 23 million acres of agricultural land, an area equivalent in size to the state of Indiana, was lost to development. It also found that more than one out of every three acres of currently developed land was built on in that 25 year period. To make matters worse, prime agricultural land, those areas most suited to growing crops and the least vulnerable to erosion, were developed at a disproportionately higher rate -- 44% more -- than non-prime agricultural acreage. The states with the most total acreage lost were Texas, California, Florida, Arizona, and North Carolina. Those with the biggest losses as a percentage of their agricultural land were New Jersey, Rhode Island, Massachusetts, Delaware, and New Hampshire.

On the bright side, the rate of loss of farmland slowed in the last five years of the survey period, compared to previous years, a drop that is attributed in part to the trend toward building single family homes on smaller lots.

The Farmland Information Center is a partnership between the USDA Natural Resources Conservation Service and American Farmland Trust that serves as a clearinghouse for information about farmland protection and stewardship. For information on ways to help protect farmland in your state and community, including a list of resources by state, visit its Web site at: Farmland Information Center .

Fothergilla Favorites

Ask a gardener to describe the ideal landscape plant and he or she is likely to list easy care, multi-season interest, and freedom from insect and disease problems. Well, that is also a good description of fothergilla, a deciduous shrub that makes an excellent addition to landscapes in many parts of the country.

Adapted to zones 4-8, fothergilla, also known as witch alder, is a native of the eastern U.S. There are two species, dwarf fothergilla (Fothergilla gardenii) and large fothergilla (Fothergilla major), as well as a number of hybrid cultivars (Fothergilla x intermedia) that have been developed. All have fragrant, white bottlebrush flowers in early spring that begin appearing before the shrub leafs out; dark green, leathery leaves with prominent veins on a rounded, multi-stemmed shrub in summer; and eye-catching fall color in shades of red, orange, yellow, and purple. Plants range in size from about two feet tall by four feet wide for the smallest cultivars to six to ten feet tall and wide for the large species. All do best in moist, acidic, well-drained soil.

To help gardeners select from among the many choices, Longwood Gardens in Kennett Square, Pennsylvania conducted an eight year evaluation of twelve species and cultivars and rated their performance when grown in their Zone 6 gardens. Plants were rated on the basis of spring flowering, summer appearance, and fall color. The ones that received the highest overall ratings were the dwarf fothergilla species (F. gardenii), the hybrid 'Mount Airy', and the hybrid 'Sea Spray'. The evaluators also noted that, while fothergilla in the wild is found mainly in shaded locations, it flowers much more abundantly when grown in full sun.